1. Technical Field
The present invention relates to a resonating element, a resonator, an electronic device, an electronic apparatus, and a moving body.
2. Related Art
In the related art, a surface mounting type electronic device has been widely used in which a piezoelectric resonator element where an excitation electrode is formed on a piezoelectric substrate is air-tightly sealed in a package. Here, the piezoelectric resonator element uses an AT cut quartz crystal resonator element or the like which performs thickness-shear vibration and employs, for example, a thin plate into which a piezoelectric substrate is cut at a cut angle called an AT cut, by using the characteristics in which the thin plate into which the piezoelectric substrate such as a quartz crystal is cut at a predetermined angle and thickness has an inherent resonance frequency.
For example, a surface mounting type quartz crystal oscillator, in which a quartz crystal resonator element and electronic parts such as semiconductor circuit elements including an oscillation circuit which oscillates the quartz crystal resonator element are mounted in the same package and are sealed, is used as an electronic device provided with the quartz crystal resonator element, and is widely used as a reference source of a frequency or time.
JP-A-2010-50508 discloses a quartz crystal oscillator in which a quartz crystal resonator is mounted on a pedestal formed by a quartz crystal which is disposed on an electronic part and an IC so as to substantially cover an opening of a recess of a container, in order to solve the problem that stable frequency-temperature characteristics cannot be obtained since stress distortion occurs due to a difference between linear expansion coefficients of a package material and the quartz crystal, resulting from an ambient temperature variation if a quartz crystal resonator element is directly mounted on a package using a conductive adhesive or the like.
FIG. 7 is a circuit diagram illustrating an example of a voltage controlled quartz crystal oscillator in the related art. The reference sign X1 indicates a quartz crystal resonator, the reference sign A1 indicates an amplifier, the reference signs Ca and Cb indicate capacitors, the reference sign D1 indicates a variable capacitance diode, the reference sign IN indicates a control voltage input terminal, the reference sign Rd indicates a resistor for applying a control voltage, and the reference sign OUT indicates a frequency output terminal of a voltage controlled quartz crystal oscillator.
In addition, a general equivalent circuit of the quartz crystal resonator X1 is shown in FIG. 8. In FIG. 8, the reference sign L1 indicates an equivalent series inductance, the reference sign C1 indicates an equivalent series capacitance, the reference sign R1 indicates an equivalent series resistance, and the reference sign C0 indicates a parallel capacitance.
If a load capacitance (combined capacitance) of a circuit side including the amplifier A1, viewed from the quartz crystal resonator X1 is set to CL, and a capacitance ratio is set to γ(C0/C1), a variation Δf/f0 of the resonance frequency f0 depending on the load capacitance CL is represented by the following well-known equation.Δf/f0=C0/(2γ(C0+CL))
In other words, in relation to a frequency of the voltage controlled quartz crystal oscillator, the resonance frequency thereof varies depending on a variation in the load capacitance of an oscillation loop.
In addition, the variable capacitance diode D1 is a diode of which a capacitance value varies depending on a reverse voltage applied between two terminals thereof. Therefore, the variable capacitance diode D1 is inserted into the oscillation loop and a voltage applied thereto is varied, thereby controlling an oscillation frequency.
However, if the quartz crystal resonator is to be miniaturized so as to correspond to miniaturization of a recent portable telephone, an information terminal or the like, an excitation electrode of a quartz crystal resonator element is reduced. Therefore, a capacitance of a package for the equivalent series capacitance C1 or a ratio of floating capacitances between electrodes increases, and, as a result, there is a problem in that the capacitance ratio γ of the quartz crystal resonator increases, and thereby a desired frequency variable width cannot be obtained.
As a piezoelectric resonator capable of adjusting the frequency variable width, a piezoelectric resonator in which an inductor circuit pattern is provided in a package and an inductor L is connected to a piezoelectric resonator element accommodated in the package is disclosed in, for example, JP-A-2-226905. The inductor L which is inserted into the oscillation loop for this purpose is generally called an extension coil (or, simply a “coil”). This is based on a principle that, when the inductor L is connected in series to the piezoelectric resonator X1, a resonance frequency becomes lower than a frequency before the inductor L is inserted, but an antiresonance frequency does not vary, and thus an interval between the resonance frequency and the antiresonance frequency becomes spread.
However, in the piezoelectric resonator disclosed in JP-A-2-226905, a dedicated package in which the inductor circuit pattern is provided is necessary, and thus there is a problem in that a package does not have versatility.